From Nat Geo:
Photograph by Ciemon Frank Caballes, National Geographic Your Shot
The residents of Jellyfish Lake on Eil Malk—one of the Rock Islands of Palau—surround a snorkeler in their midst. The saltwater lake’s golden jellyfish, harmless to humans, spend much of their lives following the sun as it makes its daily progress across the sky. For these jellies, sunlight is essential: It nourishes the algae-like organisms that live symbiotically in their tissues.